The present invention relates to a process for increasing the filling power of tobacco. More particularly, the present invention relates to a process for expanding tobacco which includes overwetting the tobacco with water and rapidly overdrying the overwetted tobacco in a turbulent steam atmosphere.
The heretofore known expansion processes may be broadly characterized as involving penetration or impregnation of the tobacco with a blowing or puffing agent, sometimes referred to hereinafter as an "impregnant", which when removed during a subsequent expansion step generates elevated pressure in the tobacco and and thereby causes expansion of the cell volume. The impregnant may be a solid, a liquid, or a gas.
Among the impregnants which have been employed are pressurized steam, air, water, organic solvents, ammonia, carbon dioxide, combinations of ammonia and carbon dioxide, and compounds capable of liberating a gas when subjected to chemical decomposition, as by heating. Where gases or other chemicals are utilized to cause or aid in expansion, physio-chemical changes may occur in the tobacco.
Among the means disclosed for removing the impregnant to expand the cell volume are a sudden reduction in pressure, freeze-drying, convection heating, radiant transfer, and the application of a microwave field. However, some of the aforementioned processes provide only a low level of expansion.
Processes employing water as an impregnant have tended to produce a more satisfactory result with tobacco stems than with tobacco lamina filler. It may be that the greater permeability of the leaf structure permits the water impregnant to escape before substantial expansion can take place. Removal of the water impregnant has typically been effected by such techniques as freeze-drying or exposure to a microwave field. Freeze-drying is a comparatively slow and expensive approach and may result, in some instances, in a product which has an objectionable amount of tackiness because of the hygroscopicity of a film-like layer of water-extracted solids which forms on the surface of the tobacco. The use of a microwave field requires elaborate and expensive equipment and may tend to be more effective with tobacco stems than with tobacco lamina filler.
Many of the prio art processes possess various disadvantages, most of which can be generally categorized as requiring prolonged treatment, batch processing and high energy usage. The process of the present invention offers advantages over many of these prior art processes and does not require foreign agents or chemical additives to achieve the objective of significantly increased filling power by expansion of the tobacco, which may be cut filler or the like.